Effect of organic impurities on the hydrocarbon formation via the decomposition of surface methoxy groups on acidic zeolite catalysts

Jiang, Yijiao; Wang, Wei; Marthala, V. R. Reddy; Huang, Jun; Sulikowski, Bogdan; Hunger, Michael

doi:10.1016/j.jcat.2005.11.029

Cited by 93 publications

(97 citation statements)

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“…[50][51][52][53][54][55] Einige Eigenschaften der MTH-Reaktion wurden bereits früh beschrieben. [50][51][52][53][54][55] Einige Eigenschaften der MTH-Reaktion wurden bereits früh beschrieben.…”

Section: Vorarbeiten: Etappen Auf Dem Weg Zum Kohlenwasserstoffpool-munclassified

Umwandlung von Methanol in Kohlenwasserstoffe: Wie Zeolith‐Hohlräume und Porengröße die Produktselektivität bestimmen

et al. 2012

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Flüssige Kohlenwasserstoffe nehmen aufgrund ihrer hohen Energiedichte und guten Transportfähigkeit eine Schlüsselrolle in der globalen Energieversorgung ein. Eine vergleichbare Bedeutung haben niedere Alkene wie Ethylen und Propylen in der Produktion von Verbrauchsgütern. In einer Gesellschaft der Nach‐Erdöl‐Zeit wird die Produktion von Kraftstoffen und Alkenen auf alternative Quellen wie Biomasse, Kohle, Erdgas und CO2 angewiesen sein. Die Umwandlung von Methanol in Kohlenwasserstoffe, bekannt als Methanol‐to‐ Hydrocarbons(MTH)‐Reaktion, könnte eine zentrale Rolle auf diesem Weg einnehmen, weil je nach Wahl des Katalysators und der Reaktionsbedingungen gezielt Benzin (Methanol‐to‐Gasoline, MTG) oder Alkene (Methanol‐to‐Olefins, MTO) hergestellt werden können. Dieser Aufsatz beschreibt eine Reihe von industriellen MTH‐Projekten, die in den letzten Jahren realisiert wurden, sowie den aktuellen Stand der Grundlagenforschung zur Synthese und Anwendung von mikroporösen Materialien für die gezielte Veränderung von Selektivität und Lebensdauer der Katalysatoren.

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Section: Vorarbeiten: Etappen Auf Dem Weg Zum Kohlenwasserstoffpool-munclassified

Umwandlung von Methanol in Kohlenwasserstoffe: Wie Zeolith‐Hohlräume und Porengröße die Produktselektivität bestimmen

et al. 2012

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“…12 These direct mechanisms are known by their intermediates and include oxonium ylide, 13,14 carbene, 15 methane-formaldehyde, 16,17 carbon monoxide, [18][19][20] methoxymethyl, 21,22 and surface methoxy groups. [23][24][25][26] Using density functional theory (DFT) calculations, Lesthaeghe et al [27][28][29] refuted some direct mechanisms based on high activation energy barriers and highly unstable intermediates. Conversely, primary olefins were proposed to form indirectly from impurities (acetone, ethanol) in the methanol feed.…”

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Transient kinetic studies and microkinetic modeling of primary olefin formation from dimethyl ether over ZSM‐5 catalysts

Omojola

Lukyanov

Veen

2019

Int J of Chemical Kinetics

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The formation of primary olefins from dimethyl ether (DME) was studied over ZSM‐5 catalysts at 300°C using a novel step response methodology in a temporal analysis of products (TAP) reactor. For the first time, the TAP reactor framework was used to conduct single‐ and multiple‐step response cycles of DME (balance argon) over a shallow bed with the continuous flow panel. Propylene is the major primary olefin and portrays an S‐shaped profile with a preceding induction period when it is not observed in the gas phase. Methanol and water portray overshoot profiles due to their different rates of generation and consumption. DME effluent shows a rapid rise halfway to its steady‐state value leading to a slow rise thereafter because of its high desorption rates followed by subsequent reactions involving DME in further steps during the induction period. To analyze the experimental data quantitatively, nine reaction schemes were compared, and kinetic parameters were obtained by solving a transient plug flow reactor model with coupled dispersion, convection, adsorption, desorption, and reaction steps. The methoxymethyl pathway involving dimethoxyethane and methyl propenyl ether gives the closest match to experimental data in agreement with recent density functional theory studies. Gaseous dispersion coefficients of ca. 10−9 m2 s−1 were obtained in the TAP reactor. The novel experimental data validated against the transient kinetic model suggests that after the formation of initial species, the bottleneck in propylene formation is the transformation of the initial C–C bond, that is dimethoxyethane formed initially from DME and methoxymethyl groups. DME adsorption on ZSM‐5 catalyst generates surface methoxy groups, which further react with the feed to give methoxymethyl groups. These methoxymethyl groups are regenerated through a series of reactions involving intermediates such as dimethoxymethane and methyl propenyl ether before propylene formation.

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“…[9] Interestingly,Hunger and co-workers showed already in 2006 that traces of organic impurities neither have any significant influence on product distribution, nor do they govern the formation of HCP species. [10] Since then, the research groups of Hunger, [10][11][12][13][14][15] Kondo, [16] Fan, [17,18] CopØret and Sautet, [19] and Lercher [20] have provided both experimental and theoretical evidences in support of the direct mechanism during the initial stages of the MTO process. Thee arlier proposed direct MTO routes include the a) oxonium ylide,b )carbene,a nd c) methane-formaldehyde mechanisms.…”

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“…Theo bserved bands at 297, 350, 479, and 640 nm are attributed to neutral methylated benzenes,dienylic carbocationic/methylbenzenium (up to three methyl groups) ions, trienylic and methylated poly-arenium ions,r espectively. [10][11][12][28][29][30] Similarly,t he 387 nm band is characteristic for ah examethylbenzenium ion (HMB + )a nd its bathochromic shift to 414 nm with increasing time-on-stream can be explained by the further methylation of HMB + to,f or example,h epta-methylbenzenium ions. [31] We propose that the cracking of polyaromatics into trienylic carbenium species and olefins are responsible for the concomitant increase and decrease of the 479 and 640 nm bands,r espectively,a fter 10 minutes of reaction (Figures S3b).…”

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Initial Carbon–Carbon Bond Formation during the Early Stages of the Methanol‐to‐Olefin Process Proven by Zeolite‐Trapped Acetate and Methyl Acetate

et al. 2016

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Methanol-to-olefin (MTO) catalysis is av ery active field of researchb ecause there is aw ide variety of sometimes conflicting mechanistic proposals.A ne xample is the ongoing discussion on the initial C À Cb ond formation from methanol during the induction period of the MTOprocess.Byemploying ac ombination of solid-state NMR spectroscopyw ith UV/Vis diffuse reflectance spectroscopya nd mass spectrometry on an active H-SAPO-34 catalyst, we provide spectroscopic evidence for the formation of surface acetate and methyl acetate,aswell as dimethoxymethane during the MTOp rocess.A saconsequence,new insights in the formation of the first C À Cbond are provided, suggesting ad irect mechanism may be operative,a t least in the early stages of the MTOr eaction.

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Effect of organic impurities on the hydrocarbon formation via the decomposition of surface methoxy groups on acidic zeolite catalysts

Cited by 93 publications

References 31 publications

Umwandlung von Methanol in Kohlenwasserstoffe: Wie Zeolith‐Hohlräume und Porengröße die Produktselektivität bestimmen

Umwandlung von Methanol in Kohlenwasserstoffe: Wie Zeolith‐Hohlräume und Porengröße die Produktselektivität bestimmen

Transient kinetic studies and microkinetic modeling of primary olefin formation from dimethyl ether over ZSM‐5 catalysts

Initial Carbon–Carbon Bond Formation during the Early Stages of the Methanol‐to‐Olefin Process Proven by Zeolite‐Trapped Acetate and Methyl Acetate

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